i've been learning the language for over a year now, and after spending two weeks in Japan where I was speaking Japanese a lot, i've been accidentally saying a couple of things in Japanese, mostly "hai" or "arigatou", i'm not stupid enough to let whole sentences and phrases randomly come out

Yes i do sometimes i'll say "kawaii" when i see something really cute and i'll say other stuff X3 but i don't get why people people say it's annoying when we say japanese phrases but it's ok for japanese people to say english phrases like "thank you" and stuff O.o

no, unless I'm speaking to someone who can speak Japanese. As I'm actually studying it. Speaking skills are important and I do have things I practice saying but I wouldn't go and start talking to my mom in Japanese, because she can't understand me nor will try to.

No I don't. Though I sometimes do say Japanese phrases and words to my close friends, but that's because they're anime fans too. And one of them is one of those hardcore otakus. Well, not too hardcore but he's your typical "glasses-guy-that-watches-and-reads-every-anime-and-manga-there-could-be". Fortunately, he isn't elitist.